The First Year Matters: Lifestyle Behaviors and Five-Year Cardiometabolic Risk Factor Accumulation After Traumatic Brain Injury

: Background/Objectives: Traumatic brain injury (TBI) is increasingly understood as a chronic condition, but the role of early post-injury lifestyle behaviors in later cardiometabolic risk remains unclear. We examined whether lifestyle behaviors reported 1 year after injury were associated with the accumulation of common cardiometabolic risk factors by 5 years in the Traumatic Brain Injury Model Systems (TBIMS) National Database. Methods: This retrospective cohort secondary analysis included adults with followed 1-year and 5-year interviews, complete 1-year data on four behaviors, and the complete ascertainment of hypertension, diabetes or high blood sugar, and high cholesterol at both waves. The exposure was a favorable lifestyle count based on not smoking, non-heavy alcohol use, non-obese body mass index, and sports or exercise at least 10 times per month. The primary endpoint was the incident accumulation of at least two new common cardiometabolic conditions between years 1 and 5. The analytic cohort was an observed-data subset defined by follow-up retention, complete behavior data, paired outcome ascertainment, and baseline at-risk status rather than a random sample of all TBIMS participants. Results: Among 10,057 linked participants with followed interviews at both waves, 9593 were adults, 3182 had complete four-behavior exposure data, 689 had complete cardiometabolic ascertainment, and 581 formed the primary at-risk observed-data cohort. The primary endpoint occurred in 39 participants (6.7%). Each additional favorable behavior was associated with lower odds of the primary endpoint in the adjusted model (odds ratio [OR], 0.63; 95% confidence interval [CI], 0.41-0.98; p = 0.040). The results were similar after adjustment for the 1-year Functional Independence Measure cognitive score and in Firth logistic regression. Because the final cohort was selected and the number of primary events was small, the estimates should be interpreted as exploratory and may not generalize to the broader TBI population. Conclusions: More favorable 1-year lifestyle profiles were associated with lower 5-year cardiometabolic risk factor accumulation after TBI. These findings support prevention-oriented follow-up but do not establish causality or validate a prognostic score.